1. Field
This disclosure relates generally to microprocessors and, more specifically, to processors that have many cores.
2. Description
A many-core processor has multiple processing cores on the same die. As process technology scales to a very small dimension, the currently prevailing design approach of achieving high performance by increasing processor frequency is severely limited by drastically increased power consumption. One alternative design approach to achieve high performance is to distribute an application across many “small” cores that are running concurrently at slower speed than a typical “larger” core. Because each “small” core is simpler, smaller and far less power hungry than a “large” core while still delivering significant performance, this many-core based design approach can help manage the power consumption more efficiently than a large-core based design approach.
Although a many-core processor has advantages over a processor with a single core or a few large cores, it also faces many challenges as the process technology scales down to small dimensions. For example, process variations, either static or dynamic, may make transistors unreliable; transient error rates may be high since capacitance on storage nodes is small and voltages are low; and reliability over time may deteriorate as transistor degradation may become worse as time passes. Such challenges may result in situations where cores in a many-core processor that perform well during factory testing fail to perform as well as before or stop performing completely over time. This makes one time factory testing and burn-in, as applied for traditional processors, less effective to ensure reliable computing with a many-core processor over time. Therefore, it is desirable to have the ability to periodically test the performance of cores in a many-core processor during its lifetime and use the test data thus obtained to improve its performance for applications.